Cercozoa

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Cercozoa
Cercomonas sp.jpg
Cercomonas
Scientific classification
Domain: Eukaryota
(unranked): SAR
(unranked): Rhizaria
Phylum: Cercozoa
Cavalier-Smith 1998[1]
Groups[4]

Filosa

Endomyxa

The Cercozoa are a group of protists. They lack shared morphological characteristics at the microscopic level,[5] being defined by molecular phylogenies of rRNA and actin or polyubiquitin.[6]

Characteristics[edit]

The group includes most amoeboids and flagellates that feed by means of filose pseudopods. These may be restricted to part of the cell surface, but there is never a true cytostome or mouth as found in many other protozoa. They show a variety of forms[4] and have proven difficult to define in terms of structural characteristics, although their unity is strongly supported by genetic studies. Cercozoa are closely related to Foraminifera and Radiolaria, amoeboids that usually have complex shells, and together with them form a supergroup called the Rhizaria.

Types[edit]

They are sometimes grouped by whether they are "filose" or "reticulose".[7]

Filose (subphylum Filosa)[edit]

The best-known Cercozoa are the euglyphids, filose amoebae with shells of siliceous scales or plates, which are commonly found in soils, nutrient-rich waters, and on aquatic plants. Some other filose amoebae produce organic shells, including the tectofilosids and Gromia. They were formerly classified with the euglyphids as the Testaceafilosia. This group is not monophyletic, but nearly all studied members fall in or near the Cercozoa, related to similarly shelled flagellates. Other notable filose cercozoans include the cercomonads, which are common soil flagellates.

Reticulose (subphylum Endomyxa)[edit]

Another important group placed here are the chlorarachniophytes, strange amoebae that form a reticulating net. They are set apart by the presence of chloroplasts, which apparently developed from an ingested green alga. They are bound by four membranes and still possess a vestigial nucleus, called a nucleomorph. As such, they have been of great interest to researchers studying the endosymbiotic origins of organelles.

Chlorarachniophytes are sometimes considered Filosa, rather than Endomyxa, while groups such as Gromia are considered Endomyxa.[8] Filosa is apparently a monophyletic group, but Endomyxa is paraphyletic.[9]

Ungrouped[edit]

In addition, three groups that are traditionally considered heliozoans belong here: the Heliomonadida, Desmothoracida, and Gymnosphaerida, which were recently grouped into the new class of Granofilosea.[7]

Finally, cercozoans include the Phaeodarea, marine protozoa that were previously considered radiolarians.

Classification[edit]

Further information: wikispecies:Cercozoa

The exact composition and classification of the Cercozoa are still being worked out. A general scheme is:

Class Chlorarachnea Chlorarachniophyta
Class Proteomyxidea Gymnophryida, Heliomonadida, Desmothoracida, Gymnosphaerida, etc.
Class Sarcomonadea Cercomonadida
Class Imbricatea / Silicofilosea Euglyphida and Thaumatomonadida
Class Thecofilosea Tectofilosida and Cryomonadida
Class Phaeodarea
Class Ebridea Ebridea

In addition two groups of parasites, the Phytomyxea and Ascetosporea, and the shelled amoeba Gromia may be basal Cercozoa, although some trees place them closer to the Foraminifera.

The spongomonads have been included here, but more recently have been considered Amoebozoa.[citation needed]

Some other small groups of protozoans are considered Cercozoa but are of uncertain placement, and it is likely many obscure genera will turn out to be cercozoans with further study.

See also: Auranticordis

Phylogeny[edit]

Phylogeny based on Bass et al. 2009,[7] Howe etal. 2011[10] and Silar 2016.[11]

Rhizaria

 Phytomyxea 




 Vampyrellida 



Filosa

 Skiomonadea 




 Chlorarachniophyceae 




 Granofilosea 


Monadofilosa

 Metromonadea 




 Cercomonadida 




 Glissomonadida-Sainourida clade 


Ventrifilosa

 Silicofilosea 



 Thecofilosea 












 Reticulosida 




 Gromiidea 



 Ascetosporea 




Retaria

Sticholonchea




Polycystinea




Acantharea



Foraminifera









Cercozoa

Taxonomy[edit]

Phylum Cercozoa[10][11][12][13]

  • Family ?Gymnophrydiidae
  • Family ?Gymnophryidae Mikrjukov & Mylnikov 1996
  • Family ?Rhizoplasmidae Cavalier-Smith & Bass 2009
  • Order ?Gymnosphaerida Poche 1913 emend. Mikrjukov 2000 [Axoplasthelida]
    • Family Gymnosphaeridae Poche 1913 [Hedraiophryidae; Gymnidae; Wagnerellidae Poche 1913]
  • Order Reticulosida Cavalier-Smith 2003 emend. Bass et al. 2009
  • Class Gromiidea Cavalier-Smith 2003
    • Order Gromiida Claparède & Lachmann 1856 s.s.
  • Class Ascetosporea Desportes & Ginsburger-Vogel, 1977 emend. Cavalier-Smith 2009 [Aplosporidies Caullery & Mesnil, 1899; Stellatosporea; Ascetospora Sprague 1979]
    • Order Claustrosporida Cavalier-Smith 2003
    • Order Paradiniida Cavalier-Smith 2009
    • Order Mikrocytida Hartikainen et al. 2014
    • Order Paramyxida Chatton 1911 [Paramyxea Chatton 1911; Paramyxidea Chatton 1911; Paramyxa]
    • Order Haplosporida Caullery & Mesnil 1899 [Balanosporida Sprague, 1979; Haplosporidia Hall, 1953; Haplosporea Caullery 1953; Haplospora Margulis & Schwartz, 1998; Haplosporidiidea Poche, 1913; Haplosporidies Caullery and Mesnil, 1905]
  • Class Phytomyxea Engler & Prantl 1897 em. Cavalier-Smith 1993 [Phytomyxinae Engler & Prantl, 1897; Phytomyxinea Poche, 1913]
  • Class Vampyrellidea [Cristivesiculatia Page 1987 stat. nov. Cavalier-Smith 1993]
    • Order Vampyrellida West 1901 emend. Hess et al. 2012 [Aconchulinida de Saedeleer 1934 emend. Bass et al. 2009; Cristivesiculatida Page 1987]
  • Subphylum Filosa Leidy 1879 emend. Cavalier-Smith 2003

References[edit]

  1. ^ Cavalier-Smith, T. (1998). "A revised six-kingdom system of life". Biological Reviews of the Cambridge Philosophical Society. 73 (3): 203–266. doi:10.1111/j.1469-185X.1998.tb00030.x. PMID 9809012. 
  2. ^ Nikolaev SI, Berney C, Fahrni JF, et al. (May 2004). "The twilight of Heliozoa and rise of Rhizaria, an emerging supergroup of amoeboid eukaryotes". Proc. Natl. Acad. Sci. U.S.A. 101 (21): 8066–71. doi:10.1073/pnas.0308602101. PMC 419558Freely accessible. PMID 15148395. 
  3. ^ Hoppenrath, M.; Leander B.S. (2006). "Ebriid phylogeny and the expansion of the Cercozoa". Protist. 157 (3): 279–90. doi:10.1016/j.protis.2006.03.002. PMID 16730229. 
  4. ^ a b Cavalier-Smith T, Chao EE (October 2003). "Phylogeny and classification of phylum Cercozoa (Protozoa)" (PDF). Protist. 154 (3–4): 341–58. doi:10.1078/143446103322454112. PMID 14658494. 
  5. ^ Chantangsi, C. (2009). Comparative morphology and molecular evolution of marine interstitial cercozoans. PhD thesis. University of British Columbia.
  6. ^ "SYSTEMATIC BIOLOGY: CERCOZOA". Retrieved 2009-03-28. 
  7. ^ a b c Bass D, Chao EE, Nikolaev S, et al. (February 2009). "Phylogeny of Novel Naked Filose and Reticulose Cercozoa: Granofilosea cl. n. and Proteomyxidea Revised". Protist. 160 (1): 75–109. doi:10.1016/j.protis.2008.07.002. PMID 18952499. 
  8. ^ "Cercozoa". Retrieved 2009-05-21. 
  9. ^ Yasuhide Nakamura, Ichiro Imai, Atsushi Yamaguchi, Akihiro Tuji, Fabrice Not, and Noritoshi Suzuki. 2015. "Molecular Phylogeny of the Widely Distributed Marine Protists, Phaeodaria (Rhizaria, Cercozoa)". Protist 166(3):363-373. doi:10.1016/j.protis.2015.05.004. (See External links below).
  10. ^ a b Howe; et al. (2011), "Novel Cultured Protists Identify Deep-branching Environmental DNA Clades of Cercozoa: New Genera Tremula, Micrometopion, Minimassisteria, Nudifila, Peregrinia", Protist, 162: 332–372, doi:10.1016/j.protis.2010.10.002 
  11. ^ a b Silar, Philippe (2016), "Protistes Eucaryotes: Origine, Evolution et Biologie des Microbes Eucaryotes", HAL archives-ouvertes: 1–462 
  12. ^ Adl; et al. (28 September 2012), "The Revised Classification of Eukaryotes" (PDF), Journal of Eukaryotic Microbiology, 59 (5): 429–493, doi:10.1111/j.1550-7408.2012.00644.x 
  13. ^ Ruggiero; et al. (2015), "Higher Level Classification of All Living Organisms", PLoS ONE, 10 (4), doi:10.1371/journal.pone.0119248 

External links[edit]